Fuel injection apparatus for internal combustion engines



B. BISCHOF FUEL INJECTION APPARATUS FOR INTERNAL coMBUsTION ENGINES NQv'. 5, 1935.

Filed Nov. l2, 1932 Patented Nov. 5,l 1935 UNITED STATES IPATlazNT, oFFlcE FUEL INJECTION APPARATUS FOR INTER- NAL COMBUSTION ENGINES Bernhard Bischof, winterthur, switzerland Application November 12. 1932, serial No. 642,319' 1 In Switzerland November 16, 1931 2 Claims.

J This invention relates to fuel injection ap-I paratus -for internal combustion engines operating with airless or solid injection of fuel.

When, as in some known forms of injection apparatus, the injection period is terminated by releasing the pressure within the fuel supply pipe,

separate means have to be provided for effectingv such release and in addition there is a tendency at low loads or low speeds of the engine for injection to be interrupted or rendered intermittent due to the pressure of the fuel being insufficient to open the fuel injection valve. With a view to providing a fuel pressure sufficient to open the injection valve, proposals have been made to furnish the injection valve with an accumulator piston whereby the minimum quantity of fuel which can move the accumulator piston is injected at a sufficient pressure when the fuel valve `is opened. Since such arrangements however which the fuel charge is delivered by the joint action of two pressure members one of which is operated in accordance with the speed of the engine whilst the other is independent of such speed, and a fuel delivery pipe through whichv the fuel charge passes from the pump to a fuel injection valve which cuts oif communication between the delivery pipe and the Working charnber of the engine to determine the end of the injection period, the commencement of the injection period being determined by a piston or like slide valve controlling communication between the working chamber of the pump and the delivery pipe.

Thus, the tendency for injection to be interrupted Adue to the fuel pressure being insuilicient at low loads or low speeds of the engine to open the injection valve, is overcome.

One construction of fuel injection apparatus according to the invention is illustrated. somewhat diagrammatically and by way of'example in the accompanying drawing. In the construction illustrated fuel is delivered by a fuel pump I through (Cl. 12S-139) a delivery pipe 2 to a fuel injection 'valve' 3 whereby the fuel is injected into the working chamber ofthe engine (not shown). ii'uelv is drawn by the pump I from a supply pipe 4 and enters the pump through an inlet port 5 when this is uncovered by the pump plunger Ii, whereby a fuel charge flows into the working chamber 1 of the pump. Reciprocation of the plunger 6 is effected by means comprising a shaft 8 carrying a cam 9. and a spring I0 which main- 1 0;-

tains the plunger 6 in engagement with the cam 9. Thus, the plunger 6 ismoved on its compression stroke by the cam 9 and is moved on its return or suction stroke by the spring I0.

'I'he plunger 6 has an axial bore I I which com-1.5; 4

municates between the working chamber I and. an annular recess I2 in the plunger 6. The pump plunger 6 cooperates with an accumulator piston I3 theloading of which can be adjusted by means of a stud I4 bearing on a loading spring 20 I5, the piston I3 having an annular flange I 6 whereby inward movement of the piston towards the pump plunger 6 is limited.

Assuming that the fuel charge has been drawn into the working chamber 'I of the pump and the 25 plunger is moving on its compression stroke, the charge in the working chamber 'I is subjected to pressure between the plunger 6 and accumulator piston I3, the pump plunger, accumulator piston and fuel charge moving together against the 3,0:l

action of the spring I5 which is thus compressed. Shortly before the plunger 6 has reached the outer dead centre position, that is to say just before the plunger reaches the end of its compression stroke, the annular recess I 2 registers 35.?

with an outlet port I 'I through which the delivery pipe 2 communicates with the cylinder of the' fuel pump I. The pump plunger 6 and accumulator piston I3 thereupon move towards each other so as to deliver the fuel chargeA to the 40 delivery pipe 2 as hereinafter described. l Prior to the delivery of fuel to the pipe 2 from the pump I the pressure in the pipe 2 is substantially equal to that pressure in the chamber yI8 of the injection valve 3 which will permit the 4,5- loading spring I 9 to close the Vneedle `valve 20.

The pressure necessary within the chamber I8 in order to raise the needle valve 2li is,. however, greater than that required to return the'valve to its seat since as soon as the needle valve is i505l raised the. area thereof upon which the fuel pressure can act exceeds the area available for this purpose when the needleyvalve is in its closed position.'

When the outlet port I'I registers with the annu- 5 5 lar recess I2in the plunger 8 the fuel charge` tially at the speed of sound through the delivery pipe 2 to the chamber IQ of the fuel injection valve 3. When, however, the pressure wave reaches the chamber I8 it is suddenly reversed since the needle valve 20 is not yet raised from its seat, so that the pressure where reversal occurs, i. e. within the chamber`I8, will be substantially double that in the deliverypipe 2. In order therefore to raise the needle valve the pressure to which the fuel within the working chamber 1 of the pump is subjected need not exceed a value which lies between the pressure necessary for closing the needle valve 20 and that necessary to raise this valve from its seat. Thus. assuming, for example, that the closing pressure of the needle valve is 300 atmospheres and, for the purpose of avoiding premature opening of the valve, the spring I9 and needle valve 20 are constructed so that the opening pressure of the needle valve is 400 atmospheres, a static pressure in the pump chamber 1 of approximately 50 atmospheres above the closing pressure will be sufficient for the pressure wave to raise the needle valve 20.

As soon as the valve is raised from its seat the area of the needle upon which the fuel can act is increased and the needle valve will be returned to its seat when injection is complete and the pressure in the chamber I8 has fallen to a value which will permit the spring I9 to close the valve, the needle valve thus determining the end of the injection period. During the return or suction stroke of the plunger 6 this closes the outlet port I1 and the accumulator piston I3 returns to its seat, that is to say to its innermost position limited by the flange I6. Continued movement of the plunger 6. on its suction stroke produces a reduction of pressure in the working chamber 1, thereby drawing in a new charge of fuel, and the cycle is repeated.

lIl'or the `purpose of regulating the quantity of fuel delivered the plunger 6 is provided with an oblique control edge 2| and a toothed rim 22 formed on an end cap `23, the teeth on the rim 22 being engaged by a worm 24 carried on a reduced to a pressure approximately half way-- between the closing pressure and the opening pressure of thefuel injection valve so that the delivery pressure can be maintained within moderate limits even when the opening pressure of the injection valve has to be high, without the risk of injection being interrupted at low loads or low engine speeds. Further. the use of a member in the form of a piston valve for controlling the point at which fuel delivery commences obviates the necessity for Ireductions or increases in the dimensions of the delivery pipe. The pressure impulse or wave is thus transmitted through the outlet port and throughout the length of the delivery pipe without partial reversals or weakening of the impulse which would 5 be liable to result if the commencement of fuel delivery were controlled, for example, by a poppet or like valve. 'Ihe static pressure of the wave, that is to say the fuel pressure within the pump when delivery commences, need be only slightly 10 greater than the mean value of the two pressures, namely the fuel pressure obtaining in the fuel injection valve prior to injection and the pressure necessary to open the injection valve.v

The pressure members, that is to say the mem- A15 bers under the joint action of which the fuel delivery to the delivery pipe takes place, may be constituted by opposed pistons either of which may serve as a slide valve to control the commencement of fuel delivery so that the provision 20 of means external to the pump for controlling the commencement of fuel delivery is rendered unnecessary.

Since the pressure of the impulse or wave is not affected either by friction or by variations in g5 the dimensions of the passages through which l the fuel flows from the pump to the injection vvalve the pressure wave will ensure opening of the fuel injection valve even at small loads or when a small quantity of fuel is to be injected 30 at each injection. The closing pressure of the needle valve is considerably lower than the opening pressure so that premature closing of the injection valve is prevented. Further, when the needle valve closes at the end of injection, open- 35 ing of the valve before the next injection with consequent leakage of fuel into the combustion chamber of the engine is obvlated without providing for release of the fuel pressure within the delivery pipe which release would necessitate reo lling of the delivery pipe prior to each injection.

If desired, the mean delivery pressure may be higher for low loads than for high loads and the point at which fuel delivery commences may be adjusted and the delivery pressurev regulated by 45 separate regulating devices. Again, the fuel delivery may be controlled by a separate slide valve or piston valve arranged in the fuel delivery pipe, instead of by the pump plunger itself. In the case of -multicylinder engines; a separate fuel 50 pump may be provided for supplying fuel to each working chamber, the several pumps being, if desired, combined as a single unit with a common drive and common regulating means. Alternatively, a single fuel pump may supply fuel to 55 several injection points through a distributor. At high loads, or when a large quantity of fuel is to be injected at each injection, means, such for example as throttling or by-pass devices may be brought into operation to damp the pressure so wave in the delivery pipe as desired. Similarly the pressure wave may be rendered ineffective at high loads by bringing into communication with the delivery pipe or with the injection valve one or more pipes having closed ends so as to damp the wave. When damping means such, for example, as throttling or by-pass devices or closed-ended pipes are provided these may be brought into communication with the delivery pipe or injection valve automatically in accordance with the load on the engine. The injection valve may be so constructed and loaded that its natural period of vibration will exceed that of the pressure wave transmitted through the deliver! Pipe 'l5 I claim:

1. In a. liquid fuel injection apparatus for internal combustion engines, the combination of a fuel pump having a. plunger driven by the engine and also provided withvan accumulator piston, an injection valve for delivering the fuel to the working chamber of the engine adapted to be opened by the fuel pressure but whose opening pressure is greater than the static pressure produced'by the pump when the pump is delivering relatively small charges of fuel, a fuel conduit between the chamber of said pump and said injection valve, and a timing valve of the slide type opening a direct passage from said pump chamber into said fuel conduit whereby longitudinal vibration of the fuel in said conduit is set up by the opening of the timing valve which causes a compressural wave in said liquid of sufficient magnitude to open the injection valve.

2. In a liquid fuel injection apparatus for internal combustion engines, a combination of a fuel pump having a plunger driven by the engine and also provided with an accumulator piston, an injection valve for delivering the fuel to the working chamber of the engine adapted to be 5 opened by the fuel pressure but incapable of being opened by the static pressure produced by said pump when the pump is delivering relatively small charges of fuel, a fuel conduit between the chamber of said pump and said injection valve 10 adapted to facilitate the transmission of longitudinal vibrations in the fuel therein to said valve, and a timing valve on said pump plunger opening a direct passage from the pump chamber into said fuel conduit whereby longitudinal vibration 15 of the fuel in said conduit is set up by the opening of the timing valve which causes a compressural wave in said liquid of suilicient magnitude to open the injection valve.

BERNHARD BISCHOF. 

